Previous work has shown that the paraventricular nucleus of the hypothalamus (PVN) is a critical brain site for the control of feeding behavior. In addition, we and others have found that estrogenic stimulation of the PVN is sufficient to lower food intake and body weight in ovariectomized females. The proposed experiments will extend the investigation of the neuroanatomical locus of the estrogenic suppression of food intake, and will also examine a possible biochemical mechanism underlying this hormone-behavior relationship. Specifically, it is hypothesized that the effects of estorgens on eating can be attenuated by lesions of the PVN, and that the estrogenci suppression of food intake is dependent upon changes in protein synthesis within neurons of the PVN. It is also hypothesized that lesions of the PVN will not prevent the facilitation of lordosis by estradiol. Experiment 1 will evaluate the behavioral responsiveness of ovariectomized rats with PVN lesions to peripheral injections of estradiol. In experiment 2, inhibitors of protein or RNA synthesis (e.g., anisomycin, actinomycin-D) will be directly applied to the PVN of ovariectomized rats given peripheral injections of estradiol. In this way we will be able to evaluae the importance of protein synthesis within the PVN for estrogen-iduced changes in eating, and investigate one possible biochemical mechanism underlying this phenomenon. The results of these experiments will hopefully confirm and extend previous findings which indicate that the PVN is an important brain region for the estrogenic suppression of food intake. Future studies could then examine the interactions between estrogens, catecholamines, and neuropeptides in the PVN so that the exact biochemical substrate for the effects of estrogens on feeding could be more clearly specified. These experiments have important implications for understanding the mechanisms underlying endocrine-related eating disorders such as anorexia nervosa and some forms of obesity. In addition, information from these studies will contribute to our understanding of brain mechanisms involved in feeding behavior.